This application is based upon and claims benefit of priority of Japanese Patent Application No. 2000-193150 filed on Jun. 27, 2000, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a sensor device having a semiconductor chip diced out from a semiconductor substrate having plural chips formed thereon and to a manufacturing process of such a sensor device.
2. Description of Related Art
Semiconductor sensor chips manufactured by dicing a substrate having plural sensor chips formed thereon are known hitherto. The sensor chip includes stationary electrodes and movable electrodes facing the stationary electrodes. Both electrodes form a variable capacitance which varies according to a dynamic force such as an acceleration force imposed on the sensor chip. The sensor chip detects the dynamic force based on the capacitance of the sensor chip.
However, there has been a problem caused by dusts generated in the dicing process of the conventional sensor chips. That is, swarfs (dicing dusts) scattered in the dicing process enter into the sensor elements such as the movable electrodes. Such swarfs cause a malfunction in the sensor operation.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved sensor chip which is kept free from the dicing dusts. Another object of the present invention is to provide a manufacturing process in which the dicing dusts are prevented from entering into semiconductor sensor elements.
A protecting sheet is pasted on a first substrate surface on which plural sensor chips are formed, and then the substrate is diced from a second surface of the substrate thereby to separate the plural sensor chips into individual pieces. The sensor chip includes a beam structure composed of a pair of stationary electrode portions and a movable electrode portion. The beam structure forms a pair of capacitances which vary in accordance with a dynamic force such as an acceleration force imposed on the beam structure.
To prevent dicing dusts (swarfs) generated in the dicing process from being scattered and entering the sensor chip, a groove surrounding the sensor chip is formed on the first substrate surface. The width of the groove is made sufficiently wide so that the protecting sheet can be bent along the side walls and the bottom wall of the groove. The sensor chips are diced out from the substrate along the groove. Since no space in which the dicing dusts scatter is formed between the protecting sheet and the bottom wall of the groove, the sensor chip is kept free from the dicing dusts. Thus, the sensor malfunction otherwise caused by the dicing dusts is prevented.
Alternatively, a peripheral bank surrounding the groove may be further formed, and the dicing may be performed along the peripheral bank. In this case, the peripheral bank and the sensor portion inside the grooves are electrically connected. Since no space is formed between the protecting sheet and the peripheral bank, the dicing dusts are prevented from scattering.
According to the present invention, the dicing dusts do not scatter in the dicing process, and the sensor chip is kept free from the dicing dusts. Thus, the sensor malfunction due to the dicing dusts is avoided.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.